Glycosaminoglycans and fibrillar collagen in priapulida: a histo- and cytochemical study

Abstract

The distribution of glycosaminoglycans and fibrillar collagen was studied in various tissues of priapulids, which represent an ancient group of marine metazoa. Sulphated glycosaminoglycans, as demonstrated at the electron microscopical level by Cupromeronic blue, were predominantly found in the cuticle, in basement membranes and also in the narrow connective tissue space below epidermis and anterior intestine. On the basis of their morphology the Cupromeronic blue precipitates could be divided into several groups. Fibrillar collagen occurred in the connective tissue under the epidermis and the epithelium of the anterior intestine. The spatial interrelationship between fibrillar collagen and glycosaminoglycans lacked with some exceptions, the high regularity found in connective tissues of other invertebrates and of vertebrates. This might be related to the special skeletal system of priapulids, consisting mainly of a strong extracellular cuticle and the turgor of the fluid-filled body cavity. In such a system the usual supportive structures seem to be of less functional significance.

Are palaeoscolecids ancestral ecdysozoans?

“…A system of large, helically wound cross-wise fibers is restricted among extant ecdysozoans to the cuticle of nematomorphs and some nematodes, which consists largely of the structural protein collagen (Schmidt-Rhaesa et al 1998)Fa putative synapomorphy of Nematoida (Nielsen 2001) (for uncertainties surrounding the precise fiber chemistry in nematomorphs see Brivio et al 2000;Protasoni et al 2003). Other ecdysozoans exhibit predominantly chitinous cuticles (Ehlers et al 1996), although collagen has been reported from the basal cuticle layers of some priapulids (Welsch et al 1992). Also, it is worth noting that fibers of equivalent helical arrangement and proteinaceous (presumably collagenous) composition are believed to have arisen multiple times in cylindrical metazoans, including among annelids, nemerteans, sipunculans, chaetognaths, and even burrowing amphibians (Seymour 1983;Ahnelt 1984;Bresciani 1991;O'Reilly et al 1997).…”

Electron microscopical localization of chitin in the cuticle of Halicryptus spinulosus and Priapulus caudatus (Priapulida) using gold-labelled wheat germ agglutinin: phylogenetic implications for the evolution of the cuticle within the Nemathelminthes

“…Whereas the cortical layer probably consists of non-collagenous proteins (see Anya 1966;Fujimoto and Kanaya 1973), the basal layers of the body cuticle are made up largely of collagens or collagen-like proteins (see Anya 1966;Cox et al 1981;Lee 1977;Leuschner et al 1979;Shepherd et al 1972). In the basal layer, these collagens are associated with glycosaminoglycans such as hyaluronic acid or chondroitin sulphate (see Anya 1966), as has also been observed in some species of the Priapulida (see Welsch et al 1992).…”

“…This indicates, that the labelling rests on polymers of N-acetyl-D-glucosamine rather than glycoproteins or glycosaminoglycans. Nevertheless, such glycosaminoglycans as heparan sulphate have been demonstrated in the endocuticle of H. spinulosus, P. caudatus and Priapulus tuberculatospinosus Baird, 1868 (see Welsch et al 1992). But the prevention of any label and disintegration of the endocuticle after chitinase treatment, in combination with the control incubation on PBS which does not diminish the labelling, indicates the presence of chitin in all endocuticular layers.…”

Application of cationic probes for the ultrastructural localization of proteoglycans in basement membranes

“…A general picture emerges for the localization of HSPGs in the glomerular basement membrane (see Fig. 3 for references): they are predominantly located in the lamina lucida externa (the epithelial side of the lamina densa, if the lamina lucida is considered an artifact; see above) and (to a smaller extent) the lamina lucida interna (the endothelial side of the lamina Callagher, 1986;Nanchahal andRiches, 1991 Reale et al, 1983;Van Kuppevelt et a]., 1985;Vernier et al, 1992Scott, 1980Call and Hollyfield, 1990;Welsch et al, 1992Chardin et al, 1990Landemore et al, 1991Schurer et al, 1978Vernier et al, 1983Luft, 1971Vaccaro and Brody, 1979;Reale et al, 1983Hunziker et al, 1983Hagiwara, 1992;Chardin et al, 1992 Shepard andMitchell, 1976a;Lullman-Rauch, 1989Shepard and Mitchell, 1976b, Reale et al, 1983Chen andWight, 1984 Shepard andMitchell, 1981;Chen and Wight, 1984;Brandes and Reale, 1990Revel, 1964Khan and Overton, 1970Spicer et al, 1978Sannes, 1984;Nanci, 1992 Kanwar andFarquhar, 1979a;Reeves et al, 1980;Nanchahal andRiches, 1991 Skutelsky andRoth, 1986;Goode et al, 1991Goode et al, , 1...…”